A Mobile Display Processor (MDP) blends multiple layers to compose a single image to be sent to a display within a wireless communication device (WCD). Some example WCDs include cellular or satellite radiotelephones, radiotelephone base stations, computers that support one or more wireless networking standards, wireless access points for wireless networking, PCMCIA cards incorporated within portable computers, direct two-way communication devices, personal digital assistants (PDAs) equipped with wireless communication capabilities, and the like.
Several different applications operating within the WCD may send information to the display at any given time. For example, a system application may send a signal strength indicator to the display while a video application may send decoded video. In some cases, the same application may send multiple display items to the display at the same time. The video application, for example, may send the decoded video plus a video counter and video control buttons. The video application may also send a decorative border that frames the decoded video. As another example, the system application may send the signal strength indicator plus a clock to the display. Each of the display items sent by the applications operating within the WCD may comprise a separate display layer.
Typically, only one of the display layers sent from the applications to the display changes at a high rate, such as the decoded video from the video application operating within the WCD. For example, the decoded video may change at a rate of approximately 30 frames per second. The remaining display layers sent to the display may change at a much lower rate or never change. For example, the time-of-day information and video counter may change at a rate of approximately 1 frame per second. In addition, only small sub-sections of the slowly changing display layers may change.
The MDP blends the different display layers together to form a single image for the display, and updates the single image according to the rate of the fastest changing display layer. For example, if the decoded video changes at a rate of approximately 30 frames per second, the MDP reads in and blends all of the display layers at the rate of approximately 30 frames per second. Reading all of the display layers from a memory within the WCD at a high rate may require a large amount of bandwidth.